Fluid-tight wall element and vessel made thereof



R- NOEL.

FLUID-TIGHT WALL ELEMENT AND VESSEL MADE THEREOF led Nov. 7. 1966 eoaem NOE Byi M" Arronneyg United States Patent Int. Cl. B013 3/00 1/20; F16j 11/06 US. Cl. 23285 5 Claims ABSTRACT OF THE DISCLOSURE A pressure vessel Wall construction having an inner layer made of material resistant to deterioration when exposed to a gas capable of diffusing therethrough, a perforated outer layer made of ordinary material and dimensioned to resist pressure, and two intermediate layers each consisting of sheet material having a system of elongated slots, the slots of respective systems running across each other and venting through the outer layer.

This invention has essentially for its objects a fluid-tight solid enclosure or partition wall element capable of resisting deterioration by a diffusing agent, separating at least two media of which at least one is fluid and capable,v under certain physical conditions, of diffusing through said wall or partition, as well as the various applications resulting from the use of this element.

It is known that hydrogen under high pressure and temperature conditions diffuses as a rule through the wall of containers containing it, or through partitions confining or retaining it. This is observed for instance in containers for operations for handling products or materials likely to generate or release hydrogen, such as hydrogen compounds or the like, by means of chemical reactions leading for example to the synthesis of ammonia or urea. In the case of metal walls or more particularly steel walls, this diffusion phenomenon is generally attended by a deteriorating action modifying the properties, characteristics or qualities, particularly of mechanical strength, which frequently leads, for most steel grades, to an increased brittleness thereof, which may even cause an untimely rupture under-Q strain. Adding chromium and molybdenum will protect steels from this increased brittleness, and the higher the hydrogen pressure and temperature, the greater these additions. Therefore, a solution for the manufacture of such apparatus utilized in chemical engineering would consist in using, for the entire wall thickness, a steel alloy having chromium and molybdenum contents sufficient to prevent the wall from becoming brittle as a consequence of hydrogen diffusion. This solution has the considerable drawback of being relatively costly due to the high cost of steel alloys, which on the other hand have relatively poor mechanical properties.

It is the scope of this invention to eliminate or remedy the above-mentioned drawbacks by avoiding or'at least limiting, in the constitution of pressure-resisting walls, the use of costly steels having insuflicient or relatively poor mechanical properties. To this end, a'wall elemept according to the invention comprises at least three s uccessively adjacent layers, namely a first end layer of a coherent material resisting preferably specifically to; a deteriorating, for example brittleness-generating, action of the aforesaid diffusing medium or agent, and in direct contact therewith, a second layer having a sufiicient mechanical resistance to the pressure of said diffusing medium, and provided with exhaust, release or draining Patented Jan. 6,. 1970 passages, ducts or orifices, and a so-called intermediate collecting layer interposed in abutting relationship between the other two and capable of transmitting mechanical stress to said second end layer and provided with means for causing any point of the interface between said first end layer and collecting layer to communicate freely with the nearest exhaust orifice of said second end layer.

According to another feature of this invention, the aforesaid collecting layer comprises holes or perforations distributed substantially throughout the surface area and preferably uniformly, to constitute at least two substantially parallel sheets or layers contiguous or juxtaposed in the thickness direction, the relative configuration, position and orientation of the two superposed systems of perforations being such that each through-hole or one sheet communicates freely with all the others through those of the other sheet.

Thus, due to this arrangement, which is of the multiple-layer type, known per se, the function of the aforesaid intermediate or collecting layer is to collect and lead towards the release, exhaust or drain holes formed in the second end layer the fluid, gaseous fluid such as hydrogen, which has diffused through the first end layer, so that the inner face of said second end layer cannot be subjected at any point to a substantial hydrogen pressure. As already stated, this collecting layer further transmits to the second end layer all the mechanical stresses resulting from the pressure exerted by the gaseous fluid against the first end layer.

The invention also relates to the various applications resulting from the use of the aforesaid device, particularly in the construction of enclosures, vessels, tanks, vats, cisterns, reservoirs, basins, caissons, or containers or similar hollow bodies having a wall closed under pressure capable of resisting corrosion or the deterioration by certain gaseous fluids having a high internal pressure and possibly a high temperature, such as hydrogen, and which may be used for example for storing, preserving or transporting substances, or more particularly apparatus constituting a reactional closed or confined space for treating hydrogen compounds through chemical reactions, or as a whole having a content likely to consist at least in part of hydrogen or any fluid having a similar diffusing and corroding or brittleness-generating properties. In a container or apparatus according to the invention the first aforesaid end layer constitutes the inner surface of said container.

Other features and advantages of the present invention will appear more clearly as the following detailed description proceeds with reference to the diagrammatic drawings attached hereto and given by way of example only; in the drawings:

FIGURE 1 is a fragmentary cross-sectional view of a wall of a container according to one form of embodiment of the invention;

FIGURE 2 is a fragmentary plane view from above of a perforated sheet constituting one of the two components of the aforesaid collecting layer;

FIGURE 3 is a fragmentary plane view from above showing the arrangement of the two perforated sheets constituting the aforesaid collecting layer;

FIGURE 4 illustrates on a larger scale a cross-sectional detail view of one portion of the aforesaid wall.

The exemplary form of embodiment of FIGURE 1 illustrates one fraction of a wall of an apparatus or con tainer, intended for example for chemical reactions, this wall being fiat or curved (cylindrical, spherical, ellipsoidal or of any other suitable geometrical configuration) and consisting eiher of the lateral wall, or of a bottom, or even of a cover. This wall, which is designated generally by the reference numeral 1, consists of at least three successive abutting layers designated by the reference numerals 2, 3 and 4 as seen from the interior of the container or apparatus. The first end layer or inner layer 2 consists of a material capable of resisting to the brittleness-generating action of the contents for example of hydrogen. The second end layer or outer layer 4 is designed or dimensioned with a view to have an adequate mechanical resistance to the inner pressure prevailing in the apparatus or container. This outer layer 4 may have either a single structure, that is, a solid or unitary structure, or consist of a plurality of adjacent elementary layers. It is not made of a material having particular resistance to brittleness caused by hydrogen. This layer 4 has formed therethrough, substantially at right angles to its surface, a multiplicity of gas exhaust, drain or release holes, ducts, channels, orifices or passages 5 leading at one end to the outer surface 6 of said layer and at the opposite end to the interface 7 between the layers 4 and 3.

The intermediate or collecting layer 3 consisting of two superposed sheets 3a and 3b is intended for collecting and directing to the exhaust holes 5 hydrogen which has diffused through the layer 2 from the inner space 7 of the container so that no part of the face 7 of layer 4 becomes subjected to a substantial hydrogen pressure, and also for transmitting to the layer 4 the stresses due to the pressure prevailing in the space 8; a multiplicity of holes or perforations 9 are distributed through each of the two superposed sheets 3a and 3b in the layer 3 (see FIGURE 4) so that any point of the interface 10 between layers 2 and 3 communicates with the exhaust orifices of layer 4. The holes 9 constitute a preferably substantially regular perforation systems in each sheet 3a, 3b. In order to enable the collecting layer 3 to permit the free flow of hydrogen between any point of face 10 of layer 2 and the nearest exhaust hole 5 in layer 4, the holes 9a and 9b of the two aforesaid regular systems are preferably shaped and disposed in staggered relationship in each system so as to partially overlap one another, thus enabling each perforation to communicate freely with all the others. To this end, various solutions may be adopted and the form of embodiment illustrated constitutes one of the various possible arrangements. In this form of embodiment, the holes of each regular system advantageously consist of identical and oriented parallel to a same direction in the elongated holes, slots or the like, preferably substantially system contemplated. These slots are preferably distributed into substantially parallel longitudinal files in which they are disposed at spaced intervals, the successive files of a same system being alternatively shifted for example by a same amount from one another, the mutual orientation of the two systems being such that the common directions of their slots are secant to each other.

In the form of embodiment illustrated the aforesaid files of slots are substantially equally spaced in each system with the same relative spacing in the two systems and their common directions are substantially perpendicular, the dimensions of the slots of the two systems being such that said slots partially overlap. FIGURE 2 illustrates the configuration of the slots or perforations in either system and FIGURE 3 shows the superposition of the two systems with directions of their respective slots 9a and 9b substantially orthogonal.

The collecting layer 3 may advantageously consist of at least two coupled perforated plates or sheets, for example of preferably relatively thin stainless steel, of a thickness of, say, one millimeter.

It has been shown that the condition necessary and sufficient for causing each perforation of a layer or sheet 3a or 3b to communicate freely with all the others through the medium of'the perforations of the other'sheet 3b or 3a, without any restriction as to the relative position of the perforation systems in relation to each other, provided that their general slot directions be substantially at right angles, is as follows, assuming I to be the length of each slot, 1 the longitudinal pitch of the perforation in each file of slots and d th transverse pitch of he perfor ion,

i.e. the mutual spacing of the files which are not shifted in relation to each other (see FIGURE 2), one must have:

As a rule, the mutual shift of two successive files of slots in each system aforesaid will be substantially equal to one-half of the longitudinal pitch p/2 of the slot in one file, whereby the preceding condition means that the length of the mutuality registering portions of two adjacent slots pertaining to two successive, mutually shifted files, must be greater than the transverse spacing or pitch of the non-mutually shifted files. In fact, with a the length of the mutually registering portions of two adjacent files pertaining to two successive, mutually shifted files in a same network, and b the relative spacing of two successive slots in a file, one may write:

b=p-l, and l=2a+b, from which we obtain a=lp/2 whereby the preceding unequality is equivalent to the following one: a d.

In FIGURE 4, which is a sectional view taken substantially along the longitudinal axis of symmetry of a slot 9b of sheet 3b, the interfaces 7 and 10 are shown in the form of gaps or interstices to illustrate somewhat exaggerately the fact that the contacts between the three layers 2, 3 and 4 are not perfect, in that there is no adherent molecular contact. The operation of this system is particularly simple and efiicient. The hydrogen diffused through the layer 2 is collected by the four slots 9b of the layer or sheet 3a which are covered by the slot 9b of the layer or sheet 3b,-whereby the hydrogen is rapidly drained through the nearest exhaust orifice 5 of layer 4. Thus each slot 9 in the layer or sheet 3a communicates with a next slot of the layer or sheet 3b.

In the rather improbable case where certain points of the sheet or layer 3a are in molecular or perfect contact with the layer 2, the small quantity of hydrogen diffused through these points would also be collected by the interstices existing or remaining between the layers or sheets 3a and 3b. Thus, obviously, the outer layer 4 cannot under any conditions contact the hydrogen under pressure, thus substantially eliminating any risk or possibility of causing a brittleness increment.

Of course, the invention should not be construed as being limited by the specific form of embodiment described and illustrated which is given by way of example only.

What I claim .is:

1. A substantially impervious solid wall element, serving as a partition between two media at least one of which contains a component agent capable of diffusing through said wall element, comprising three superposed mutually adjacent layers, namely: a first layer for placing in direct contact with said agent containing medium and made of coherent material capable of resisting a deteriorating action when exposed to diffusion of said agent therethrough, a second layer spaced from the first layer for placing in direct contact with the other medium and having a system of holes formed therethrough, and an intermediate collecting layer sandwiched between the first and second layers, and composed of a plurality of mutually adjacent sub-layers, each sub-layer consisting of sheet material having a system of through-perforations in. the shape of elongated slots, the slots of one sub-layer being arranged to run across slots of a sub-layer adjacent thereto, and the holes of said second layer forming outlet passages leading from the slots of the Sub-layer adjacent thereto to said other medium.

2. A wall element according to claim 1, wherein the slots of a sub-layer are mutually parallel and arranged in parallel files.

3. A wall element according to claim 2, wherein the slots of a sub-layer run perpendicular to the slots of a sub-layer adjacent thereto.

4. A Wall element according to claim 3, wherein the slots of each file are equally spaced therein at a pitch common to all said files, and wherein the slots of a file are staggered relatively to the slots of files adjacent thereto.

5. A wall element according to claim 4, wherein the amount of stagger is equal to one half of said pitch.

6 References Cited UNITED STATES PATENTS 1,188,530 6/1916 Bosch 232 9 2,217,090 10/1938 Zerbe 2203 X 5 2,243,240 5/1941 Zerbe 2203 X 2,600,630 6/1952 Fergusson 2203 X 3,231,338 1/1966 Andrus 23290 MORRIS O. WOLK, Primary Examiner 10 SIDNEY MARANTZ, Assistant Examiner U.S. C1.X.R. 

